1. Field of the Invention
This invention relates to an exercise machine, more particularly to an elliptical exercise machine which permits the user to exercise by moving his/her feet along an elliptical path.
2. Description of the Related Art
Referring to FIG. 1A, a typical elliptical exercise machine includes a frame 11 which carries a pair of swinging arms 16, a pair of foot members 14 connected to a wheel 12 through cranks 13, and a pair of reciprocating members 17 each of which is connected to one of the swinging arms 16. The foot members 14 are provided respectively with foot platforms 15. The bottom ends of the foot members 14 are slidable along rails provided on the frame 11. When the user stands on the foot platforms 15 and makes an exercise by moving the foot platforms 15 with his feet, the foot members 14 move forward and rearward, and the cranks 13 rotate about the axis of the wheel 12 so that each foot platform 15 ascends and descends along an elliptical path.
However, since the foot platforms 15 are mounted fixedly on the foot members 14, they are immovable relative to the foot members 14. The immovable foot platforms 15 are inflexible and are therefore unable to change their inclining position according to the varying inclining position of the user' feet during the course of exercising movement. Therefore, the foot platforms 15 are unable to contact and support the entire part of the user's feet which tend to incline at different inclining angles during their movements along elliptical paths. Especially, when the user's feet reach their highest or lowest position, they are unsupported at the heels so that the heels are substantially in a suspended position and are vulnerable to strain and fatigue.
U.S. Pat. Nos. 5,540,637 and 5,813,949 also disclose an exercise machine which enables a user to move his feet along an elliptical path. In this machine, foot platforms are supported by respective foot members which are not connected to a crank and which do not slide on the base of a frame. However, like the prior art shown in FIG. 1, the foot platforms of the machine disclosed in each patent are also immovable relative to the foot members so that they cannot provide sufficient support for the user's feet.
FIG. 1B shows an exercise machine including foot platforms 10 each of which is pivotal relative to a foot member 101 to which the foot platform 10 is attached. Each foot platform 10 is pivoted to a fulcrum member 103 which is mounted on the foot member 101 through a pivot pin 104 and is further connected pivotally to a reciprocating member 102 through a head part 105 of the pivot pin 104. While each foot platform 10 is pivotal to move along with the user's foot for providing good support, since it is connected to the foot member 101 only by means of the pivot pin 104 passing through the fulcrum member 103, the exercise machine, when in use, can be subjected to huge bending force and stress concentration at the joint between the foot platform 10 and the foot member 101, thereby resulting in failure of the joint or damage of the machine.